Botany is based on fixed genera.

The names of the plants ought to be stable [certa], consequently they should be given to stable genera.

If you do not know the names of things, the knowledge of them is lost, too.

A herbarium is better than any illustration; every botanist should make one.

Nomenclature, the other foundation of botany, should provide the names as soon as the classification is made... If the names are unknown knowledge of the things also perishes... For a single genus, a single name.

No one has been a greater botanist or zoologist. No one has written more books, more correctly, more methodically, from personal experience. No one has more completely changed a whole science and started a new epoch.

Nature's economy shall be the base for our own, for it is immutable, but ours is secondary. An economist without knowledge of nature is therefore like a physicist without knowledge of mathematics.